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Subject[PATCH v2] xen: issue warning message when out of grant maptrack entries
Date
When a driver domain (e.g. dom0) is running out of maptrack entries it
can't map any more foreign domain pages. Instead of silently stalling
the affected domUs issue a rate limited warning in this case in order
to make it easier to detect that situation.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
drivers/xen/grant-table.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 7bafa703a992..84575baceebc 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -1040,18 +1040,33 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
return ret;

for (i = 0; i < count; i++) {
- /* Retry eagain maps */
- if (map_ops[i].status == GNTST_eagain)
- gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
- &map_ops[i].status, __func__);
-
- if (map_ops[i].status == GNTST_okay) {
+ switch (map_ops[i].status) {
+ case GNTST_okay:
+ {
struct xen_page_foreign *foreign;

SetPageForeign(pages[i]);
foreign = xen_page_foreign(pages[i]);
foreign->domid = map_ops[i].dom;
foreign->gref = map_ops[i].ref;
+ break;
+ }
+
+ case GNTST_no_device_space:
+ pr_warn_ratelimited("maptrack limit reached, can't map all guest pages\n");
+ break;
+
+ case GNTST_eagain:
+ /* Retry eagain maps */
+ gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref,
+ map_ops + i,
+ &map_ops[i].status, __func__);
+ /* Test status in next loop iteration. */
+ i--;
+ break;
+
+ default:
+ break;
}
}

--
2.16.4
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